What's a good markup library that can parse into it?

Text::Markdown, and there are many others in that vein. Try some CPAN searches for more.

...is HTML::StripScripts as good as advertised?

Not sure. But there are alternatives. HTML::Scrubber and HTML::Sanitizer come to mind. Check them all out before "buying." I usually do my own filtering of HTML through XML::LibXML; it's fast, easy to pass around document objects, and can guarantee correctness but it's a bit more bare metal.